Many types of opto-electronic modules comprise a number of separate optical and electrical components that require precise placement relative to one another. A silicon (or glass) carrier substrate (sometimes referred to as an interposer) is generally used as a support structure to fix the location of the components and may, at times, also provide the desired electrical or optical signal paths between selected components. As the components are being assembled on the interposer, active optical alignment may be required to ensure that the integrity of the optical signal path is maintained. In most cases, these opto-electronic modules are built as individual units and, as a result, the need to perform active optical alignment on a unit-by-unit basis becomes expensive and time-consuming.
Indeed, as the demand for opto-electronic modules continues to increase, the individual unit assembly approach has become problematic. Wafer level packaging is considered to be a more efficient and cost-effective approach, with one exemplary arrangement of wafer level packaging disclosed in our co-pending application Ser. No. 13/463,408, filed May 3, 2012 and herein incorporated by reference.
In our co-pending application, a silicon wafer is utilized as a “platform” (i.e. interposer) upon which all of the components for a multiple number of opto-electronic modules are mounted or integrated, with the top surface of the silicon interposer used as a reference plane for defining the optical signal path between separate optical components. The use of a single silicon wafer as a platform for a large number of separate modules allows for a wafer level assembly process to efficiently assemble a large number of modules in a relatively short period of time. Some prior art arrangements describe the use of a glass interposer in place of a silicon wafer interposer, while retaining the ability to assemble multiple opto-electronic modules at the same time. See, for example, U.S. Patent Publication 2012/0106117 authored by V. V. Sundaram and published on May 3, 2012, which discloses a three-dimensional interconnect structure based upon a glass interposer.
In most cases, a “lid” needs to be placed over and attached to the populated interposer component. In one exemplary prior art arrangement, a lid is formed as two separate piece parts, a “sidewall” portion that attaches to the interposer top surface and a flat “top” portion that is bonded to the sidewall portion. The height of the sidewall is generally defined by the space required for the components disposed on the interposer, as well as a layer of adhesive material used to bond the sidewall to the interposer. In other cases, the sidewall is defined by a combination of a “rim” formed on the interposer and a “rim” formed on the lid, where the two rims are later joined to form the sidewall. Heretofore, the manufacture of lids provided with rims was considered to be expensive and required mechanical machining of a glass plate. This subtractive technique is expensive and ill-suited to a wafer level assembly process.